Question

Imprinting The figure depicts the maternal imprinting of the mouse Igf2 gene. CTCF H19 Igf2 000 OOO Insulator Enhancers 0000 Question 35 (2 points) a) What is an insulator? (1-Point). What is maternal imprinting? (1-Point).

Answer 1

a) What is an insulator?

Silencing of the maternal Igf2 is mediated by the action of an insulator element upstream of the H19 promoter coincident with the DMR and nuclease hypersensitive sites. When active, as on the maternal chromosome, the insulator would function in a position-dependent manner to prevent activation of the Igf2 promoter by the downstream enhancers.

What is maternal imprinting?

An example of epigenetic inheritance is parental imprinting, discovered about 15 years ago in mammals.In parental imprinting, certain autosomal genes have seemingly unusual inheritance patterns. For example, the mouse igf2 gene is expressed in a mouse only if it was inherited from the mouse’s father. This is an example of maternal imprinting because a copy of the gene derived from the mother is inactive..

b? What is the mechanism of maternal imprinting for the Igf2 gene?

In humans (and other mammals like mice and pigs) the IGF2 allele inherited from the father (paternal) is expressed; the allele inherited from the mother is not.Methylation of an imprint control region will tell you about whether its maternally or paternally imprinted.

The level of methylation generally correlates with the transcriptional state of a gene: active genes are less methylated than inactive genes. We have seen that bacterial chromosomes are methylated, but this example
illustrates that occasional bases of the DNA of higher organisms are methylated as well (exceptions include
yeast and Drosophila).

What is the mechanism by which the paternal allele is not imprinted?

Mothyl group CH NS EC Methytransferase NS4 Cytosine

Because a copy of the gene derived from the mother is inactive.Hence the paternal allele is not imprinted.Only one of the two homologs is active for this gene.Here,the maternal copy is inactive owing to imprinting.

Maternal lgfr2 allele transcribed lgir2 CpG island 990 Paternal gfr2 allele not - transcribed Igr2